The present invention relates to copper-base spinodal alloys and, in particular, copper-base spinodal alloys also containing nickel and tin.
Ternary copper-nickel-tin spinodal alloys are known in the metallurgical arts. As one example, U.S. Pat. No. 4,373,970 discloses spinodal alloys containing from about 5 to 35 weight percent nickel, from about 7 to 13 weight percent tin, and the balance copper. The alloys disclosed by this prior art patent exhibit in the age hardened spinodally decomposed state a highly desirable combination of mechanical and electrical properties, i.e. good strength and good electrical conductivity, and thus have valuable utility as a material of construction for articles of manufacture such as electrical connectors and relay elements. One particular ternary spinodal alloy composition falling within the scope of the disclosure of U.S. Pat. No. 4,373,970 contains about 15 weight percent nickel and about 8 weight percent tin and is sold commercially under the trade name of Pfinodal (Pfizer Inc.; New York, N.Y.). This alloy composition combines a sufficient strength for many commercial applications with a good ductility and an excellent electrical conductivity. When greater strength properties than those afforded by the Cu-15Ni-8Sn alloy composition are required for certain other applications, this can be realized by raising the nickel and tin levels within the ranges for those elements disclosed in U.S. Pat. No. 4,373,970. However, this increased strength tends to be achieved at the expense of the valuable ductility, formability and electrical conductivity properties of the age hardened spinodally decomposed alloy.
Other copper base spinodal alloys containing nickel and tin are disclosed in U.S. Pat. Nos. 3,937,638; 4,012,240; 4,090,890; 4,130,421; 4,142,918; 4,260,432 and 4,406,712. Of particular interest is U.S. Re. Pat. No. 31,180 (reissue of U.S. Pat. No. 4,052,204), which discloses the addition of small amounts of iron, zinc, manganese, zirconium, niobium, chromium, aluminum and magnesium to copper-nickel-tin spinodal alloys in order to improve mechanical and working properties. However this prior art patent does not disclose the use of cobalt as an additive element and does not suggest the use of a quaternary spinodal alloy system to obtain an improved electrical conductivity.
Quaternary copper-nickel-tin-cobalt alloys are disclosed in U.S. Pat. Nos. 3,940,290 and 3,953,249. These alloys contain only 1.5% to 3.3% tin and thus do not appear to be spinodal alloys. Furthermore, these prior art patents teach that the cobalt level in the alloy should not exceed 3% in order to minimize impairment of ductility and hot workability.